Head-mounted displays (HMD) have long been proven invaluable for many applications, spanning the fields of scientific visualization, medicine, and military training, engineering design and prototyping, tele-manipulation and tele-presence, and personal entertainment systems. In mixed and augmented reality systems, optical see-through HMDs are one of the basic approaches to combining computer-generated virtual scenes with the views of a real-world scene. Typically through an optical combiner, an optical see-through head-mounted display (OST-HMD) optically overlays computer-generated images onto the real-world view while maintaining a direct, minimally-degraded view of the real world. An OST-HMD presents a great potential for creating a mobile display solution that offers much more attractive image quality and screen size than other popular mobile platforms such as smart phones and PDAs (personal digital assistants). There exist many technical and practical difficulties preventing the technology from being widely adopted.
Modern computing and display technologies have facilitated the development of systems for so called “virtual reality” or “augmented reality” experiences, wherein digitally reproduced images or portions thereof are presented to a user in a manner wherein they seem to be, or may be perceived as, real. A virtual reality, or “VR”, scenario typically involves presentation of digital or virtual image information without transparency to other actual real-world visual input; an augmented reality, or “AR”, scenario typically involves presentation of digital or virtual image information as an augmentation to visualization of the actual world around the user.
When placing digital content (e.g., 3-D content such as a virtual chandelier object presented to augment a real-world view of a room, or 2-D content such as a planar/flat virtual oil painting object presented to augment a real-world view of a room), design choices may be made to control behavior of the objects. For example, the 2-D oil painting object may be head-centric, in which case the object moves around along with the user's head (e.g., as in a Google Glass approach); or the object may be world-centric, in which case it may be presented as though it is part of the real world coordinate system, so that the user may move his head or eyes without moving the position of the object relative to the real world.
As a result, a question or design choice often arises as to whether the object should be presented as world centric (i.e., the virtual object stays in position in the real world so that the user may move his body, head, eyes around it without changing its position relative to the real world objects surrounding it, such as a real world wall); body or torso centric, in which case a virtual element may be fixed relative to the user's torso, so that the user may move his head or eyes without moving the object, but such movement is slaved to torso movements; head centric, in which case the displayed object (and/or display itself) may be moved along with head movements, as described above in reference to Google Glass; or eye centric, as in a “foveated display” configuration wherein content is slewed around as a function of the eye position.
Conventional stereoscopic displays provide binocular disparity that supports convergence on any point but only allows the viewer to accommodate on the display surface and thus suffer from accommodation-convergence conflict. These convention displays often decouple the accommodation cue from the convergence cue and tie the accommodation cue to a fixed distance. Thus, there exists a need for methods and system for image displaying stereoscopy with a freeform optical system with addressable focus for virtual and/or augmented reality.